Autism is a severe and chronic neuropsychiatric disorder that typically reveals itself in the first 36 months of life. While individual behavioral profiles can vary widely, there are core domains revealing deficits in social interaction and relations, language and communication skills, and behavioral control. Twin studies and high sibling relative risk ratios indicate a strong genetic component to this disorder, which was once thought to be rare, but autism spectrum disorders are now thought to have a 1/250 prevalence or more. Genetic studies have been challenged by sample heterogeneity and limited by small sample sizes. This supplement to parent grant 1 R01 MH64547-01, "A Genome Wide Search for Autism Susceptibility Loci," supports the efforts of the Autism Genetic Resource Exchange (AGRE), a large collaborative effort to create a bank of genotypic and phenotypic data from multiplex autism families and to share this data with the scientific community. Specifically, this supplement would fund the recruitment, collection of biomaterials, and state-of-the-science phenotypic profiling (ADI-R, ADOS, Peabody Picture Vocabulary Test, Raven Progressive Matrices, Vineland Adaptive Behavior Scales, and medical history and neurological exams) of 400 North American multiplex families affected by autism. The work will be carried out by the AGRE team of diagnosticians, clinicians, administrators and phlebotomists under subcontract to the University of California, Los Angeles. In order to facilitate recruitment and accommodate the strained circumstances of multiplex families, the majority of diagnostic work is done in the family home. Biological samples (DNA, cell lines, and serum) are placed in the NIMH repository and all phenotypic data is placed in an internet accessible database maintained by the Autism Genetic Resource Exchange. Data are marked only with a confidential sample ID so that families remain anonymous and data become immediately available, with no holdback period, to the entire scientific community through approved access to the password-protected databases for biomaterials and/or phenotypic data. This effort accelerates recruitment, exceeds previously stated goals for sample size and, by adding to the already substantial number of previously collected families pledged by AGRE to the NIMH repository, creates the world's largest and most powerful genetic resource for the study of autism. This work is a direct response to Title 1 of the Pediatric Health Act of 2000 which authorizes and mandates an increased NIH commitment to autism gene banking. [unreadable] [unreadable]